[Valgrind-developers] [valgrind] s390x: Add missing early-clobber to GET_STARTREGS

[Andreas A. <ar...@so...>]

https://sourceware.org/git/gitweb.cgi?p=valgrind.git;h=943669f4ea16381154ec0cb26237e901d34e6d83

commit 943669f4ea16381154ec0cb26237e901d34e6d83
Author: Andreas Arnez <ar...@li...>
Date:   Wed Oct 9 17:10:08 2024 +0200

    s390x: Add missing early-clobber to GET_STARTREGS
    
    The inline assembly for GET_STARTREGS in m_libcassert.c writes to its
    output before using the input argument.  But since the compiler doesn't
    know this, it is allowed to allocate the same register for both, causing
    problems.  This has been seen when compiling Valgrind with -O0, after
    which memcheck/tests/leak-autofreepool-5 fails due to SIGSEGV.
    
    Fix this by declaring the output as early-clobber, so the compiler knows
    about the restriction.

Diff:
---
 coregrind/m_libcassert.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/coregrind/m_libcassert.c b/coregrind/m_libcassert.c
index db9d43d874..257c26bc63 100644
--- a/coregrind/m_libcassert.c
+++ b/coregrind/m_libcassert.c
@@ -177,7 +177,7 @@
            "std %%f5, 64(%1);"                            \
            "std %%f6, 72(%1);"                            \
            "std %%f7, 80(%1);"                            \
-           : /* out */   "=r" (ia)                        \
+           : /* out */   "=&r" (ia)                       \
            : /* in */    "a" (&block[0])                  \
            : /* trash */ "memory"                         \
         );                                                \